Over the past several years, various medical devices have been developed which are designed to be implanted in a patient's body. Such devices are useful, for example, for stimulating internal body tissue (e.g., muscle, nerve, etc.) for a wide variety of medical applications. Many of these devices include a battery which can be recharged from an external power source via either a hard wire connection or wirelessly, e.g., via an alternating magnetic field. Although various battery technologies have been used, the lithium ion battery has evolved to generally be the battery of choice for implantable medical devices.
Under certain malfunction conditions, such as an internal or external electric short, a rechargeable lithium ion battery can produce a temperature excursion of 120° C. or more. A temperature of this amplitude can cause significant damage to body tissue.